1. Field of the Invention
The present invention relates to a radiating direction control unit of a lighting device for vehicle use in which a change in the level of a front or rear wheel axle is detected and a radiating direction of the lighting device for vehicle use is controlled according to a change in an attitude of the vehicle.
2. Related Art
There is known an automatic leveling device, which is a device for automatically correcting a radiating direction of a beam of light emitted from a lighting device (head lamp) incorporated into a vehicle so that the radiating direction of a beam of light can be kept in a predetermined direction at all times.
For example, an automatic leveling device, in which one vehicle leveling sensor is used, is composed as follows. There is provided a leveling sensor in one of the axles of a front and a rear wheel. A change in the level of the axle concerned is detected, and a change in the pitch angle of the vehicle body is estimated by the change in the level. A reflecting mirror arranged in a head lamp is driven so that the change in the level can be canceled. In this way, the radiating direction of the lighting device and the height of a cut line on a light distribution pattern can be controlled. In this device, it is a precondition that the pitch angle of a vehicle can be explicitly determined with respect to a change in the level of the axle which is detected by one vehicle leveling sensor.
However, in the conventional device, the following problems may be encountered. In the case where a change in the level is caused which does not affect the pitch angle in the running attitude of a vehicle, for example, in the case where the vehicle is turned and rolling occurs in the vehicle, the leveling sensor detects a change in the level of the axle, and a radiating direction of the lighting device is changed by the detected change in the axle. In this case, the radiation angle is controlled not in accordance with a change in the pitch angle of the vehicle.
For example, when the leveling sensor is attached to a left rear axle, the level of a left rear wheel is increased in the case where the vehicle is turning to the left. When it is erroneously recognized that this change is the same as that of a case in which a front portion of the vehicle is lowered, that is, when it is erroneously recognized that this change is a nose dive, the radiating direction of the lighting device is controlled so that this change can be canceled. That is, the radiating direction of the lighting device is controlled so that the radiating direction of the lighting device is controlled upward with respect to a horizontal face. Accordingly, there is a possibility that a beam of light directed upward at this time causes a glare in an opposed car. When the vehicle is turning to the right, the level of the left axle is lowered. Therefore, it is erroneously recognized that this change is the same as that in the case where the front portion of the vehicle is shifted upward. In this case, the radiating direction of the lighting device is controlled downward with respect to a horizontal face. Therefore, visibility of the vehicle is lowered in this case. That is, there is a possibility that safety of driving is impaired.